The crucial role for the first gata-1 site in the exon1 of CCR3 in its transcription

Abstract

GATA-1 is shown to regulate development/differentiation of myeloid lineages including eosinophils. CCR3 is almost exclusively expressed on eosinophils and has been extensively studied for a molecular target to interfere eosinophils-associated diseases such as asthma. There are several putative gata-1 sites in exon1 of CCR3 and the regions flanking the exon1. To know whether GATA-1 is involved in CCR3 expression and further which gata-1 site is responsible for GATA-1 binding, we performed chromatin immunoprecipitation assay and mutation analysis using peripheral blood eosinophils, developing eosinophils, and cell lines that express varying degrees of CCR3 and GATA-1. We found that GATA-1 strongly bound to the regions in the exon1 and the intron1 downstream the exon1. K562 cells, which endogenously express the highest level of GATA-1, exhibit much higher CCR3 reporter activity than cells expressing low or intermediate levels of GATA-1. Introduction of DN-GATA-1 resulted in a decrease in CCR3 reporter activity. Among eight point mutants for the gata-1 sites, the first gata-1 sequence of exon1 is solely responsible for CCR3 transcription, which was subsequently confirmed by EMSA.